Facebook has hit 2 billion active monthly users, Chief Executive Mark Zuckerberg announced Tuesday. The social media giant has doubled its user base in less than five years — it reached 1 billion in October 2012.

Growth has held largely steady during that time. In its most recent earnings report, Facebook said it had 1.94 billion monthly active users as of March 31, up 17% from a year earlier. Daily active users rose too: There were 1.28 billion on average in March, up 18%.

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The achievement finds the company reflecting on its role as an influencer and a moderator. It's been a tough stretch for companies that thrive on user-generated content, and Facebook Inc. is no exception.

The social network has taken fire for the spread of propaganda and "fake news," and for the continued existence of extremist and hateful speech on its platform.

"We feel like our responsibility is expanding, especially around passing this milestone of 2 billion people in the community," Zuckerberg told reporters last month at Facebook's headquarters in Menlo Park, Calif.

Facebook has been deleting 288,000 posts a month as part of its effort to crack down on hate speech, the company announced in a blog post Tuesday.

Facebook defines hate speech as "anything that directly attacks people based on what are known as their 'protected characteristics' — race, ethnicity, national origin, religious affiliation, sexual orientation, sex, gender, gender identity, or serious disability or disease."

The post said Facebook is a long way away from using artificial intelligence to effectively detect hate posts, and it still relies on users to report potential violations.

The social media giant said it employs 4,500 moderators and plans to add 3,000 by next year.

Zuckerberg has said the extra vetting won't be enough to solve the issue entirely.

"No matter how many people we have on the team, we'll never be able to look at everything," Zuckerberg said in an earnings call in May.

Critics of the company's approach — including nearly 80 rights organizations and the British prime minister's office — have said Facebook needs to clearly define its methodology for dealing with issues of hate and extremism.

Facebook's rules and guidelines for policing posts had previously been a secret, but last monththe Guardian published leaked PowerPoint slides and documents that it said the company sends to moderators.

The guidelines in those documents highlight the complicated nature of censorship. One slide outlawed posts containing the phrase "Someone shoot Trump" because the president is protected as a head of state, but allowed the phrase "I hope someone kills you" because it's either generic or not credible.

The guidelines also allowed some videos of violent deaths because they can help spread awareness about mental health issues.

Facebook said its moderators respond to millions of flagged posts every week.